Recently, electronic devices, portable electronic devices in particular, have remarkably been evolving, with which development of batteries having a high energy density has been in demand. As such a battery, lithium-ion secondary batteries have widely been employed as power supplies for portable devices because of their very high energy density and the like. A lithium-ion secondary battery is mainly constituted by a cathode, an anode, a separator, and a nonaqueous electrolytic solution, whereas various studies have been made in order to further improve battery characteristics.
For example, preferred as a nonaqueous solvent for the nonaqueous electrolytic solution is one having a relatively low melting point, a relatively high conductivity, a relatively wide potential window (electrochemical window), and a capability of yielding a high ionic conductivity even at a low temperature when an electrolyte is dissolved. From this viewpoint, propylene carbonate has favorably been in use. When provided with a negative electrode (anode) using a carbon material such as highly crystallized graphite as a constituent material, however, propylene carbonate has been problematic in that its decomposition proceeds in a cathode (an electrode which functions as a negative electrode at the time of discharging) at the time of charging in particular.
When the decomposition of propylene carbonate proceeds, a gas is generated, with which the carbon material of the negative electrode peels off, decomposes, etc., thereby causing problems of decrease in capacity and gradual deterioration in battery characteristics such as charging/discharging cycle characteristic while in use. As the decomposition of propylene carbonate progresses, decomposition products are deposited on the negative electrode, which also seems to gradually deteriorate the battery characteristics mentioned above.
Therefore, batteries aimed at restraining the decomposition reaction of propylene from proceeding by adding 1,3-propane sultone or 1,4-butane sultone into a nonaqueous electrolytic solution using at least propylene carbonate as an ingredient of the nonaqueous solvent have been proposed (see, for example, Japanese Patent Application Laid-Open Nos. 2000-3724 and 2000-3725).
Also, a battery preventing electrolysis from occurring on the negative electrode surface of propylene carbonate by adding 1,3-propane sultone into a nonaqueous electrolytic solution using a mixed solvent of propylene carbonate, ethylene carbonate, and diethyl carbonate has been proposed (see, for example, Japanese Patent Application Laid-Open No. HEI 11-339850).
Further, batteries aimed at restraining the decomposition reaction of propylene carbonate from progressing by adding vinylene carbonate into a nonaqueous electrolytic solution using at least propylene carbonate as an ingredient of the nonaqueous solvent have been proposed (see, for example, Japanese Patent Application Laid-Open Nos. HEI 11-67266 and 2000-58125).
Furthermore, a battery aimed at restraining the decomposition reaction of propylene carbonate from progressing by adding 1,3-propane sultone and vinylene carbonate into a nonaqueous electrolytic solution using at least propylene carbonate as an ingredient of the nonaqueous solvent has been proposed (see, for example, Japanese Patent Application Laid-Open No. 2001-43895).